Electron tube with anode-heated cathode



July 13, 1965 z. N. HOF 3,195,058

ELECTRON TUBE WITH ANODE-HEATED CATHODE Filed June 5, 1963 ZYGMUNT N HOF INVENTOR.

BY gag s AGENT United States Patent Office 3,l5,@58 Patented July 13, 1965 3,95,058 ELECTRGN TUBE WITH AWGBE-HEATED CATHODE Zygninnt N. Hof, 9 Willow Place, Mount Vernon, NX. Filed June 5, 1963, Ser. No. 285,811 Claims. (Cl. 328-252) This invention relates to electron tubes and more particularly to electron tubes of high efiiciency with integrated anodes and cathodes.

The performance of an electron tube is limited by the heat dissipated in the anode or plate. Heat is produced in the anode by the impact of the electrons on its surface and by the plate current passing through the resistance represented by its body. This heat is removed from the anode by radiation and also by convection, e.g. by forcedconvection cooling in the case of large tubes. Since this heat is dissipated, its energy is lost for the specific purpose for which the tube is designed. At the same time a certain amount of electrical energy must be supplied to the tube during its operation in order to heat the cathode to a temperature which brings forth the emission of electrons and to apply a voltage to the anode which will maintain a current of electrons between the cathode and the anode apart from any signal and biasing voltages impressed upon other electrodes which are of no further interest here. Only a part of this energy is converted into a useful output, the remainder being again wasted as heat.

The ratio of useful output to total input of electrical energy is defined as the efliciency of the electron tube.

In electron tubes of conventional construction the dis sipation of heat in the anode results not only in a reduction of the efiiciency of such tubes but also in a limitation of the plate current as that current must be kept below a magnitude that would heat the anode to a destructive temperature.

it is an object of my invention to provide means for decreasing the heat dissipation and increasing the efficiency of electron tubes.

It is another object of my invention to provide means for increasing the permissible anode current of electron tubes.

It is still another object of my invention to provide an electron-tube unit in which the heat produced in the anode is not wastefully dissipated but eifectively utilized.

It is a more specific object of my invention to provide an integrated electron tube in which the heat energy produced in the anode of one of its units is used to heat the cathode of another of its units.

It is still a further object of my invention to provide simple electric circuits for the operation of such a tube.

In accordance with my invention I provide an electron tube comprising at least two integrated units each having an electron-emitting cathode and an electron-receiving anode. I make the anode of one unit to serve as the cathode of a second unit by applying a coating of electron-emissive material to the anode of the first unit. I also provide a circuit which initiates an electron current between the cathode and the anode of the first unit. By this current the anode of the first unit is heated and as it heats up the coating on it emits electrons. These electrons are attracted and received by the anode of the second unit by virtue of a positive potential provided at the latter anode through an external circuit from the output of the first unit.

Other features of my invention relate to the provision of auxiliary electrodes in my electron tube along with external circuits as required for the operation of the several units of the tube.

My invention will be best understood from the following description of a specific embodiment, given with reference to the accompanying drawing in which:

FIG. 1 is a partly cut-away elevational view of the interior of an electron tube constructed in accordance with my invention;

FIG. 2 is a cross-sectional view of the interior of the electron tube taken on the line II-II of FIG. 1; and

FIG. 3 is a circuit diagram of a system for the operation of an electron tube of the type illustrated in FIGS. 1 and 2.

FIGS. 1 and 2 show the interior of one embodiment of an electron tube 7 according to my invention in which, within an evacuated envelope (seen diagrammatically in FIG. 3), two indirectly heated rod-shaped cathodes 1 and 1' are mounted inside an anode 2 of suitable material. The anode 2 has the shape of an elliptical cylinder and the cathodes 1, 1' are located substantially along the focal axes of the cylinder.

The two cathodes 1, 1' and the anode 2 constitute the electrodes of a rectifier diode.

The body of diode anode 2 is coated externally, i.e. on its side remote from the cathodes, with a thick layer 3 of electron-emissive material which has a high ratio of emission current to heating power. Provided that the anode 2 becomes heated sulficiently, this layer 3 will emit electrons and therefore acts as the cathode of another tube section further comprising a grid electrode 5, which surrounds the cathode 3 over approximately three-fourths of its axial length, a bias anode 4 which surrounds the cathode 3 over approximately one-fifth of its length, and a main anode or plate 6 which surrounds the grid 5. The electrodes 3, 5 and 6 thus constitute the electrodes of a triode.

In FIG. 3 I have shown a circuit arranged in accordance with my invention for the operation of the electronic tube described and illustrated above. Electrical energy for the operation of the electron tube 7 is supplied through a power transformer 9 whose input terminals 17, 17 are connected across an alternating-current source 18. Signal energy is supplied to the triode unit of the electron tube 7 at the input terminals 14, 15 tied, respectively, to the triode grid 5 and the triode cathode 3. The grid bias is provided by the resistors 12, 13 and derived from the smoothed D.-C. output of the filter 16. The useful output of the electron tube 7 consists of the amplified signal energy which is obtained at the output terminals 24, 25 of a signal-receiving load 23, here shown as an output transformer, and also of unmodulated electric energy which is obtained as direct current, after rectification by the diode cathodes 1, 1 and the diode anode 2, at the D.-C. output terminals 26, 27.

In the system schematically illustrated in FIG. 3, the diode cathodes 1, 1' are mounted as sleeves over heater wires which are traversed by alternating current from supplemental windings 8, 8 of the power transformer 9. The cathode sleeves 1, 1' coated with electron-emissive material are connected to opposite ends of the high-voltage winding 10 of the power transformer 9. The high voltage between these ends and the center tap of the winding 10 is applied to a resistance 20 and normally closed contacts 22 of a thermal relay 21 to the diode anode 2 and, alternatingly, to the diode cathodes 1, 1', the resulting fullwave rectification giving rise to a continuous current which passes through the filter network 19 so that a well-smoothed direct current is obtained at the leads terminating at 26, 27. Network 19 also applies the required D.-C. potential between the cathode 3 and anode 6 of the triode section of the tube as is evident from FIG. 3.

During the operation of the elctron tube 7, electrons from the diode cathodes 1 and 1' impinge on the diode anode 2 and cause it to heat up. The triode cathode 3 is the only medium through which heat from the anode 2 can be dissipated since the cathode 3 shields the anode 2 thermally and is in immediate thermal contact therewith, practically all the heat of the anode 2 enters the cathodefi and both will be at the same temperature. 'In order to heat anode 2 and, simultaneously, cathode 3 to a temperature which will bring forth a continuous electron emission from the cathode 3 sufiicient for the operation of the electrodes 3, 4, 5, 6, the electron current from the diode cathodes 1, 1 to diode anode 2 is suitably adjusted by the spacing of and the voltage applied between the diode electrodes, and by the value of the resistance 29.

It should be noted that for the purpose of a sufiiciently large emission from the triode cathode 3 the diode anode 2, made of a material which'is thermally and electrically capable of sustaining the impact of the electrons and of supporting the electron-emissive layer, is given the shape of an elliptical cylinder, with the diode cathodes 1, 1' in its focal axes, in order to achive a uniform distribution of electron currents from these cathodes to anode 2 and, thus, a uniform heating of the anode 2. I

It should also be noted that, as the heating of the anode 2 takes place over the entire exposed surface of the large-area anode 2, the emission from cathode 3, which is integral with anode 2, occurs along an equally large area. In prior tubes the cathode emission has been limited by the small emissive area of the cathode so that the heating power supplied to the heater wires could not be fully utilized, but in an electron tube constructed in accordance with my invention the electron-emissive surface of the cathode 3 can be designed so that the maximum possible electron emission per unit of area is realized with full utilization of the thermal energy supplied by the heat abstracted from anode 2.

As further shown in FIG. 3, the main'triode electrodes 3, 6 of the electrontube 7 are connceted across the D.C. output terminals 27, 26. Triode cathode 3 is connected to the negatively polarized terminal 27 whereas the triode anode 6 is connected to the positively polarized terminal 26 through the signal receiver 23 and the thermal relay 21. As soon as the electron current between triode cathode 3 and triode anode 6 substantially balances the direct current flowing through ballast resistance the triode anode 6 and the contacts 22 are opened so that current no longer flows through the resistance 20.

It should be noted that, in this way, current passes through the resistance 20 only for a very short period in order to initiate the heating of diode anode 2 and, thereby, the electron emission from cathode 3. Therefore the total energy dissipated in the resistance 20 during the operation of the elctron tube 7 is negligible. After resistance 26 is cut out of the circuit, heating continues by the normal rectifier action. The energy which is dissipated in the thermal relay 21 is also made insignificant by proper design of the relay. The lead circuit connected across the electrodes 3, 6 of the second tube section in series wtih the rectifying output connection 26, 27 is entirely passive, i.e. it does not include any additional source of current to supplement the D.C. energy derived from the supply source 9, 18 of the first tube section 1, 1, 2.

A bias potential is developed between triode cathode 3 and triode grid through a half-wave rectification circuit comprising a low-voltage winding 11 on the power transformed 9, from which an alternating voltage is applied between the bias anode 4' and, via a potentiometer 12, the triode cathode 3. After rectification by the triode cathode 3 and the bias anode 4 and after filtering by a network 16, a continuous voltage appears at the terminals of potentiometer 12 so that the lead from signal input terminal 15, connected to cathode 3, is at a positive e'ntial while a negative potential is tapped from extraneous heat to one of the cathodes.

the slider 12d of potentiometer 12 and applied by way of an isolating resistance 13 to the lead from signalinput terminal 14 which extends to the triode grid 5.

'By displacing the ta 12a on the potentiometer 12, the

drawing that the partial loss of electric energy sup-' plied to the herein disclosed electron tube is smaller than in the systems of prior art because no heat is dissipated from one of the anodes; neither is it necessary to supply Thus, my novel electron tube and circuit achieve an improvement in efficiency as compared with conventional tubes in which heat is dissipated from each anode and in which it is necessary to supply thermal energy to each cathode.

Furthermore, in the electron tube and circuit according to my invention not only do I use the heat dissipated in one of the anodes to heat one of the cathodes but the same current which is the primary source of this heat also serves to drive allother anodes. As can be seen from the instant disclosure, the maximum permissible electron current received by the combination anodecathode structure of the tube (i.e. the magnitude of that current which can be tolerated without giving rise to destructive temperatures) is larger than in electron tubes of the prior art because the heat liberated in the anode by the plate current is used up almost entirely and continuously for the electron emission from the cathode. Thus, any accidental increase in anode current will result to a major extentin an increase in electron emission from the cathode and to a minor extent only in an increase in the temperature of the integrated electrodes. Therefore, as the variation of electrode temperature caused by a Variation of plate current is. smaller than in the anodes of conventional electron tubes, a greater electron current directed to the integrated anode-cathode structure of my electron tube is permissible than in the prior art.

' Finally, the electron-emissive area of the integrated anode-cathode structure according to my invention is relatively-larger than that of conventional cathodes and allows for one more parameter to be selected in its design as compared with the prior art, namely, for the adaptation of the electron-emissive area of the cathode to the available heating power.

It is to be understood that'my invention is not limited to the combination of diode and triode specifically disclosed but that, at least in accordance with its broader aspects, the two tube sections sharing a common electrode structure, acting as an anode for one section and as a cathode for the other, may be of a variety of'types known per se and may include any number of grids and/or other auxiliary electrodes. Thus, the first tube section could also be. supplied with direct rather than alternating current and connected, for example, to operate as an oscillator whereas the second tube section might be, for instance, a multigrid power amplifier, e.g.

' of the dual-plate type conventionally used in push-pull circuits. These and othermodifications, which will be readily apparent to persons skilled in the art, are therefore intended to'be embraced in the spirit and scope oftheinvention except as otherwise limited by the appendedclaims. I

' I claim:

1. In an electron tube having an evacuated envelope, in combination, a first tube section and a second tube section in said envelope, said first tube section including an electron-emissive first cathode and a first anode, said second tube sectionincluding an electron-emissive second cathode and a second anode, said first anode beingdisposed adjacent said second cathode in heat-transmitting relationship therewith, an energizing circuit including a source of current connected across said first cathode and said first anode, said energizing circuit being provided with a rectifying first output connection having two conductors, a passive load circuit including a second output connection connected across said second cathode and said second anode; said energizing circuit being provided with a ballast resistance bridged across said conductors of said first output connection, current-responsive relay means in said load circuit having contacts for opencircuiting said ballast resistance in response to flow of an electron current of predetermined minimum magnitude between said second cathode and anode.

2. In an electron tube having an evacuated envelope, in combination, a first tube section and a second tube section in said envelope, said first tube section including two electron-emissive first cathodes and a first anode, said second tube section including an electron-emissive second cathode and a second anode, said first anode being disposed adjacent said second cathode in heat-transmitting relationship therewith, an energizing circuit including a source of alternating current connected across said first cathodes and returned to said first anode, said energizing circuit being provide-d with a direct-current first output connection, and a load circuit including a second output connection connected across said second cathode and said second anode, said first anode being substantially in the shape of an elliptical cylinder, said first cathodes being in the form of rods substantially disposed along the focal axes of said cylinder.

3. The combination defined in claim 2 wherein said second tube section is provided with a control grid and with a signal-input circuit connected across said grid and said second cathode, said signal-input circuit including rectifying means for deriving a biasing potential from said source of alternating current.

4. The combination defined in claim 3 wherein said rectifying means includes an auxiliary anode in said second tube section.

5 In an electron tube having an evacuated envelope,

in combination, a first tube section and a second tube section in said envelope, said first tube section including two electron-emissive first cathodes and a plate-shaped first anode having a side proximal to said first cathodes and a side remote therefrom, said second tube section including a second cathode and a second anode, said second cathode being constituted by an electronemissive coating on said remote side, an energizing circuit including a source of alternating current connected across said first cathodes and returned to said first anode, said energizing circuit being provided with a direct-current first output connection, and a passive load circuit including a second output connection connected across said second cathode and said second anode in series with said first output connection, said second tube section being provided with a control grid, a signal-input circuit connected across said grid and said second cathode, and grid-biasing means in said signal-input circuit in cluding an auxiliary anode forming part of a rectifying connection across said source of alternating current, said first anode and second cathode, control grid, auxiliary anode and second anode being in the shape of nested cylinders of substantially elliptical configuration, said first cathodes being in the form of rods substantially disposed along the focal axes of the cylindrical first anode.

References flied by the Examiner UNlTED STATES PATENTS 1,210,678 1/17 Nicholson 313-305 X 1,303,579 5/19 Nicholson 31330-5 X 1,309,704 7/19 Stoekle 313-305 X 1,655,270 1/28 Hull 313305 X 1,864,591 6/32 Foster 313-305 X 2,002,207 5/35 MacLaren 328-452 X 2,348,814 5/44 Herriger 313-305 DAVID J. GALVIN, Primary Examiner.

JAMES D. KALLAM, Examiner. 

2. IN AN ELECTRON TUBE HAVING AN EVACUATED ENVELOPE, IN COMBINATION, A FIRST TUBE SECTION AND A SECOND TUBE SECTION IN SAID ENVELOPE, SAID FIRST TUBE SECTION INCLUDING TWO ELECTRON-EMISSIVE FIRST CATHODES AND A FIRST ANODE, SAID SECOND TUBE SECTION INCLUDING AN ELECTRON-EMISSIVE SECOND CATHODE AND A SECOND ANODE, SAID FIRST ANODE BEING DISPOSED ADJACENT SAID SECOND CATHODE IN HEAT-TRANSMITTING RELATIONSHIP THEREWITH, AN ENERGIZING CIRCUIT INCLUDING A SOURCE OF ALTERNATING CURRENT CONNECTED ACROSS SAID FIRST CATHODES AND RETURNED TO SAID FIRST ANODE, SAID ENERGIZING CIRCUIT BEING PROVIDED WITH A DIRECT-CURRENT FIRST OUTPUT CONNECTION, AND A LOAD CIRCUIT INCLUDING A SECOND OUTPUT CONNECTION CONNECTED ACROSS SAID SECOND CATHODE AND SAID SECOND ANODE, SAID FIRST ANODE BEING SUBSTANTIALLY IN THE SHAPE OF AN ELLIPTICAL CYLINDER, SAID FIRST CATHODES BEING IN THE FORM OF RODS SUBSTANTIALLY DISPOSED ALONG THE FOCAL AXES OF SAID CYLINDER. 